16,654 research outputs found
Monitoramento e modelagem do processo de interceptação da chuva de uma bacia coberta por floresta ombrófila mista
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Ambiental, Florianópolis, 2015.A interceptação é o processo pelo qual a precipitação que cai sobre a superfície do terreno fica retida, é redistribuída ao solo ou evapora posteriormente. Esse processo é importante especialmente em áreas florestais, pois influencia na reciclagem da umidade do ar e também na quantidade de água que efetivamente chega ao solo. A maioria dos estudos de interceptação nas florestas brasileiras foi feita na região Amazônica e Mata Atlântica, mas poucos foram os estudos realizados na Mata Atlântica do tipo Floresta Ombrófila Mista. O objetivo deste trabalho foi compreender e estimar os processos de interceptação da chuva em uma bacia coberta por Floresta Ombrófila Mista por meio de monitoramento e modelagem. A perda por interceptação (I) foi estimada por meio da medição de chuva externa (P), chuva interna (Tf) e escoamento pelo tronco (Sf). O monitoramento da chuva externa foi feito com três pluviômetros e um pluviógrafo instalados fora da bacia. Nove pluviômetros e uma calha interligada a um pluviógrafo foram instalados para o monitoramento da chuva interna. O monitoramento do escoamento pelo tronco foi realizado em dez árvores interligadas a um recipiente de armazenamento e mais quatro árvores interligadas a um pluviógrafo. Os índices de cobertura do dossel foram estimados a partir de fotografias do dossel. Os dados hidrometeorológicos foram monitorados na estação meteorológica do Rio Feio. A chuva externa nos três anos de monitoramento somou 5.309 mm distribuídos em 321 eventos e houve 489 dias sem ocorrência de chuva. Os modelos de Rutter esparso e de Gash esparso foram utilizados para a modelagem do processo de interceptação. A chuva interna variou de 61 a 83% da chuva externa, o que demonstrou que a chuva interna é heterogênea na bacia coberta por Floresta Ombrófila Mista. O volume de escoamento de tronco variou de 0,1 a 22,9 litros, com média de 2,92 litros e no período monitorado os volumes tenderam a crescer com o aumento do diâmetro do tronco e da área da copa. O índice de cobertura do dossel na bacia variou de 45 a 94%, com média de 80% e não apresentou correlação com a distribuição da chuva interna. Os dados automatizados da chuva interna e escoamento pelo tronco foram distribuídos em 60 eventos, a chuva externa foi 1.303 mm, a chuva interna e escoamento pelo tronco corresponderam a 75% (981 mm) e 2 % (19 mm) da chuva externa. A média da evapotranspiração potencial da série calculada foi de 1,09 mm dia-1. O erro relativo por evento dos modelos de interceptação variou de 2 a 400% para o modelo de Rutter e de 0 a 350% para o modelo de Gash. O modelo de Gash subestimou a I acumulada enquanto que o modelo de Rutter a superestimou. A simulação com o modelo de Rutter foi a que obteve os menores valores do erro relativo (4%) em relação a I acumulada. Os dois modelos tiveram limitações para representar o processo de interceptação em eventos extremos, possivelmente devido aos erros associados à estrutura dos modelos assim como ao conjunto de dados medidos e estimados.Abstract :The interception is the process by which the precipitation that falls on the ground surface is retained, it is redistributed to the ground or evaporate later. This process is important especially in forested areas since it influences recycling of moisture from the air and also the amount of water that effectively reaches the ground. Most of the interception studies in Brazilian Forests were carried out in the Amazon and Atlantic Forest, but few have been conducted in the Atlantic Forest Mixed Ombrophilous Forest type. The objective of this work was to understand and estimate the process of interception of rain in an experimental catchment covered by Mixed Ombrophilous Forest through monitoring and modeling. The interception loss will be estimated by measuring rainfall (P), throughfall (Tf) and stemflow (Sf). The monitoring consists of three rain gauges and automatic rain gauge installed outside the basin for rainfall monitoring. Nine gauges and one trough-type collectors coupled to a rain gauge for throughfall monitoring. The stemflow monitoring was conducted in ten trees connected to a storage container and four trees connected to a rain gauge. The canopy cover fraction was estimated using photographs taken of the canopy. Hydrometeorological data were acquired with a meteorological station of Rio Feio. The Rutter and Gash models were used to model the interception process. The total rainfall monitoring of the complete 3 years was 5.309 mm, from 321 rainfall events and in 489 days there was no rainfall. The throughfall ranged from 61 to 83% the rainfall, which showed the throughfall heterogeneity. The stemflow ranged from 0,1 to 22,9 liters, averaging 2,92 liters and the volumes tend to increase with the diameters at breast height and crown area increases. The canopy cover fraction ranged from 45 to 94 %, averaging 80%. The calculation of the interception loss using automated date rail and stemflow were distributed in 60 events. The rainfall (P) was 1303 mm, Tf and Sf corresponded to 75% (981 mm) and 2% (19 mm) of P. The mean potential evapotranspiration was 1.09 mm day-1. The relative error in the models for the events ranged from 2 to 400% for the Rutter model and 0 to 350% for the Gash model. The Gash model underestimated I while the simulation of the Rutter model overestimated. The simulation with the Rutter model was the one with the lowest values of relative error (4%) for I accumulated. Both models have limitations to identify the process of interception
Recent Results From the EU POF-PLUS Project: Multi-Gigabit Transmission Over 1 mm Core Diameter Plastic Optical Fibers
No full textRecent activity to achieve multi-gigabit transmission over 1 mm core diameter graded-index and step-index plastic optical fibers for distances up to 50 meters is reported in this paper. By employing a simple intensity-modulated direct-detection system with pulse amplitude or digital multi-tone modulation techniques, low-cost transceivers and easy to install large-core POFs, it is demonstrated that multi-gigabit transmission up to 10 Gbit/s over 1-mm core diameter POF infrastructure is feasible. The results presented in this paper were obtained in the EU FP7 POF-PLUS project, which focused on applications in different scenarios, such as in next-generation in-building residential networks and in datacom applications
Employing M1 direct calibration/de-embedding approaches for large signal model validation at mm-wave frequencies
No full textIn this contribution, we employ direct calibration/de-embedding approaches to validate the large signal device model of state-of-the-art HBTs and CMOS technologies operating in the mm-wave frequency band WR6. The capability of placing the first tier calibration reference plane in close proximity to the DUT allows the large signal metric to be directly compared with foundry models.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
The influence of welding parameters and parent plate metallurgical characteristics on solidification of austenitic stainless steel weld metals
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The present work reports the effect of heat input, cooling rate, parent plate deformation and restraining conditions on the formation and morphology of delta ferrite in welds on AISI 318L and 321 steels. The experiments were carried out on commercially produced plates in the following conditions: (i) as received condition (ii) further deformed by cold rolling. (iii) further deformed by hot rolling. The effect of heat input and cooling rates were examined using bead-onplate Submerged Arc welds on the same parent plate material. The parent plate condition was assessed using bead-on-plate metal Inert Gas (MIG) and Subm rged Arc butt welds. The results suggest that 1. The weld metal solidification proceeds epitaxially from the existing unmelted base metal. The weld exhibited surface marking i.e. deformation bands or close packed plane, in the austenite matrix, but not passing through delta ferrite phase. 2. The solidification substructure, the ferrite content, and morphology are influenced by tile (i) thermal stress induced during welding, (ii) parent plate chemical composition, (iii) the parent plate microstructural and deformation characteristics i.e. strain energy. 3. Rapidly cooled welds have lower ferrite content than welds produced with slower cooling rates. The randomly distributed elongeed ferrite with some lath type ferrite morphology was predominantly attributed with the welds produced with high cooling rates. 4. The ferrite is the first solidified phase to form and austenite is formed from the liquid rather than by solid phase transformation of primary ferrite to austenite. 5. The ferrite formation is a diffusion controlled phase transformation, the degree of its dendrites development depends upon the welding parameters i.e. heat input, cooling rates. 8. Two types of ferrite morphology were observed: (a) elongated type dendrites identified as vermicular by previous investigators and (b) the cellular type morphology which has not been classified in previous investigations
Dynamic Estimation of Vital Signs with mm-wave FMCW Radar
No full textIn this paper, we propose a method for continuous monitoring of vital signs-in particular, respiration frequency-with a commercial mm-wave radar. The nearly constant frequency (NCF) model is adopted to represent chest displacement due to respiration and simulate radar response. Based on this model, an extended Kalman filter (EKF) based estimator is developed to track the breathing frequency of a person. The impact of dynamic model parameters is investigated in numerical simulation. The possibility to track breathing frequency with the proposed method is demonstrated by experimental data processing. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Microwave Sensing, Signals & System
A 23-to-29GHz Receiver with mm-Wave N-Input-N-Output Spatial Notch Filtering and Autonomous Notch-Steering Achieving 20-to-40dB mm-Wave Spatial Rejection and -14dBm In-Notch IP1 dB
No full textDigital beamforming receivers (RXs) support MIMO operation and offer great flexibility and accuracy in multi-beam formation and calibration. However, compared with analog phased-array and hybrid systems, due to the absence of any rejection for spatial in-band blockers, the RX/ADC dynamic range and linearity should be high enough to prevent array saturation. Therefore, the use of self-steering spatial notch filters (SNFs) is necessary to aid the digital beamformers and reduce RX/ADC power consumption while strong blockers exist. To address that, the sub-6GHz RXs in [1], [2] synthesize a baseband spatial notch impedance and translate it to RF by passive mixers. However, this technique cannot be directly applied at mm-wave frequencies as the impedance translational performance of the passive mixers degrades significantly. Hence, the mm-wave beamformer in [3] realizes a cascadable SNF at an intermediate frequency (IF). However, the front-end mm-wave components like mixers and phase shifters have to tolerate strong blockers, thus degrading RX linearity. Besides, it uses multiple IF buffers and VGAs for signal scaling and combining, which could be power-hungry if a similar method is adopted to realize a mm-wave SNF. To improve on those limitations, we propose a scalable SNF structure, which (1) suppresses the strongest in-band blocker at mm-wave frequencies, (2) supports N-input-N-output MIMOs, and (3) requires no active blocks except the phase shifters. A two-step autonomous notch-steering technique is also developed to adjust the SNF notch direction power-efficiently and accurately.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic
Experiencing the armed struggle : the Soweto generation and after
No full textIncludes bibliographical references (p. 354-369).This study explores the experiences of the rank-and-file soldiers of Umkhonto we Sizwe and the Azanian People's Liberation Anny. Extensive interviews by the author and other researchers reveal the voices of the soldiers themselves. The African National Congress and Pan African Congress archives at the University of the Western Cape and the University of Fort Hare supplement and verify these oral testimonies, as do some published sources. Most previously published materials about the armed struggle against apartheid have already focused on diplomacy, strategy and tactics, operations, leadership, and human rights abuses to the neglect of the soldiers' actual experiences. This study complements these with significant new oral history materials from the Soweto generation of soldiers and their successors. When dealing with MK, many authors have documented issues of the camp structure in Angola, and operations inside South Africa, so much of this detail is only addressed briefly, leaving space to explore the soldiers' experiences. In the case of APLA, very little has been written on its history, and more detail is provided on these subjects. This study therefore deals with the soldiers' politicisation and motivation for joining the armed struggle, their experiences in leaving South Africa and training in exile, the crises in exile which limited their effectiveness for a time, their return to fight in South Africa, and their difficulties in the "new" South Africa. These materials reveal that vast problems remain facing these veterans of the struggle against apartheid, and that they have the potential, if properly supported and employed, to contribute substantially to the development of present day South Africa. Conversely, if their neglect continues, they also have the potential to bring vast harm to the country. Further use of the investigative tools of oral history, especially if extended to the former soldiers' vernacular languages, is necessary to augment the history of South Africa, and these soldiers' contributions
Grouped People Counting Using mm-wave FMCW MIMO Radar
No full textThe problem of radar-based counting of multiple individuals moving as a single group is addressed using an mm-wave multiple-input-multiple-output (MIMO) frequency-modulated continuous wave (FMCW) radar. This problem is challenging because the different individuals are closer to each other than the range/azimuth resolution, and their bulk Doppler signatures are difficult to distinguish, as they tend to move together. A processing pipeline is proposed, based on the combination of a multiple target tracking algorithm with a classifier to track each group and count the number of people within. Specific salient features are defined for the classifier and extracted from range-azimuth maps and cadence velocity diagrams (CVDs). The proposed pipeline has been experimentally validated in several outdoor scenarios with grouped people. The results show that the combination of tracking algorithm and classifier in the proposed pipeline outperforms alternative methods from the literature as well as a commercial toolbox for people counting.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Microwave Sensing, Signals & System
MM Recital
No full textMM RecitalEmbargo status: Restricted until 06/2172. To request the author grant access, click on the PDF link to the left
Social Signals and Multimedia: Past, Present, Future
No full textThe rising popularity of Artificial Intelligence (AI) has brought considerable public interest as well faster and more direct transfer of research ideas into practice. One of the aspects of AI that still trails behind considerably is the role of machines in interpreting, enhancing, modeling, generating, and influencing social behavior. Such behavior is captured as social signals, usually by sensors recording multiple modalities, making it classic multimedia data. Such behavior can also be generated by an AI system when interacting with humans. Using AI techniques in combination with multimedia data can be used to pursue multiple goals, two of which are high-lighted here. First, supporting people during social interactions and helping them to fulfil their social needs either actively or passively.Second, improving our understanding of how people collaborate, build relationships, and process self identity. Despite the rise of fields such as Social Signal Processing, a similar panel organised at ACM Multimedia 2014, and an area on social and emotional signal sat the ACM MM since 2014, we argue that we have yet to truly fulfil the potential of the combining social signals and multimedia. This panel asks where we have come far enough and what remaining challenges there are in light of recent global events.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pattern Recognition and Bioinformatic
- …
